A polymer electrolyte fuel cell using a proton conductive solid polymer membrane operates at a low temperature in comparison to other types of fuel cells, for example, a solid oxide fuel cell or a molten carbonate fuel cell. For this reason, the polymer electrolyte fuel cell has been expected to be used as a power source for energy storage system or a driving power source for a vehicle such as a car, and practical uses thereof have been started.
In general, such a polymer electrolyte fuel cell uses expensive metal catalyst represented by platinum (Pt) or a Pt alloy, which leads to high cost of the fuel cell. Therefore, development of techniques capable of lowering the cost of the fuel cell by reducing a used amount of noble metal catalyst has been required.
For example, Patent Literature 1 discloses an electrode catalyst having catalyst metal particles supported on a conductive support, wherein an average particle diameter of the catalyst metal particles is larger than an average pore diameter of fine pores of the conductive supports. It discloses that, according to the above-described configuration, the catalyst particles are not allowed to enter the fine pores of the supports, so as to increase a ratio of the catalyst particles used in a three phase boundary, and thus, to improve use efficiency of expensive noble metal.